As described in German Patent Application No. DE 41 07 693 or European Patent Application No. EP 04 54 943, for example, the boost pressure is usually regulated by a regulator forming a manipulated variable as a function of the difference between a setpoint boost pressure and an actual boost pressure. This manipulated variable is used to control either a valve in a bypass bridging the turbine of the exhaust gas turbocharger in the exhaust gas channel (see German Patent Application No. DE 41 07 693) or the adjustable turbine guide vanes having a variable geometry (see European Patent Application No. EP 04 54 943).
Engines are subject to ever increasing demands regarding exhaust gas and consumption parameters. An exhaust gas turbocharger having a variable turbine geometry allows an adjustment to the instantaneous engine operating point to be made by adjusting the turbine guide vanes. Using this technique, a delayed response of the exhaust gas turbocharger (turbo lag) may be reduced and at the same time the efficiency of the engine may be improved. When accelerating, often strong overshooting of the boost pressure occurs, which places high mechanical stress on the turbocharger. In addition, excessive closing of the variable turbine geometry in the acceleration phase may result in an undesirably high exhaust gas counterpressure, which negatively affects the dynamics and the efficiency of the engine.
German Patent Application No. DE 10 010 978 describes a device for regulating the boost pressure of an internal combustion engine having an exhaust gas turbocharger, whose turbine situated in the exhaust channel of the internal combustion engine has a variable geometry, the boost pressure being regulated by adjusting the turbine geometry. A regulator forms a manipulated variable for the turbine geometry as a function of the exhaust gas counterpressure prevailing in the exhaust gas channel upstream from the turbine. In this way the above-described shortcomings are satisfactorily overcome.
An object of the present invention is to provide an alternative method and an alternative device for the above-mentioned boost pressure regulation which ensure that, in the event of a change in the load, the boost pressure follows the desired variation of the boost pressure setpoint value as rapidly as possible without exceeding the boost pressure setpoint value, to protect the compressor and the exhaust gas turbocharger against unnecessarily high loads.